Graft polymerization process



United States Patent Office 3,046,078 Patented July 24, 1%2

3,046,078 GRAFT POLYMERIZATION PROCESS Jason M. Salshury, Watchung,Samuel Kaizerman, North Plainfield, and Guido Mino, Plainfield, N.J.,assignors to American Cyanamid Company, New York, N.Y., a

corporation of Maine Filed Mar. 18, 1958, Ser. No. 722,287

14 Claims. (Cl. 8-116) This invention relates to a process for treatingcellulosic materials whereby polymerizable vinyl and/ or vinylidenemonomers are graft-polymerized onto the cellulosic material in the vaporphase by use of a ceric salt as the oxidizing agent. Still further, thisinvention relates to the process of treating textile fabrics and paperwebs with a polymerizable vinyl and/ or vinylidene monomer in the vaporphase in the presence of a ceric salt whereby said monomer isgraft-polymerized onto said fabric or web.

One of the objects of the present invention is to graftpolymerize avinyl or vinylidene monomer onto a cellulosic material by maintainingthe monomeric material in the vapor phase and in the presence of a cericsalt. A further object of the present invention is to impart unusualproperties to cellulosic materials by the practice of the process of thepresent invention. These and other objects of the present invention willbe discussed in greater detail hereinbelow.

The polymerization in general of olefinic monomers within the fibers ofcellulosic materials is known in the prior art but the prior art methodshave suffered from a plurality of limitations. The most serious of theselimitations resides in the simultaneous polymerization of the monomericmaterial in the treatment bath, on the surface of the cellulosicmaterial with some small measure of the polymerization taking placeWithin the fibers themselves. This shortcoming results in a waste of themonomeric material, the production of an objectionable layer of polymeron the surface of the cellulosic material, which layer is often diihcultif not virtually impossible to remove. The instant invention is asubstantial advancement in the art over the known polymerizationtechniques of the prior art inasmuch as the polymerization can be madeto occur substantially entirely within the fibers of the cellulosicmaterial. Additionally, the polymer then deposited on the base islargely grafted to the cellulosic material and becomes an integral partof the cellulosic base material. Still further, there is no wastage ofthe monomeric material by polymerization in the vapor chamber apart fromthat taking place in the grafting mechanism on the base material. Afurther advantage of the present invention resides in the fact that theprocess can be carried out at a considerably faster rate than theprocesses of the prior art.

The cellulosic materials which may be used in the practice of theprocess of the present invention may be in the form of a fiber such ascotton fibers or a fabric either woven or unwoven such as'cotton clothor a matted web such as paper. Still further, the process of the presentinvention is applicable to films and synthetic fibers tent of at least0.5% at the temperature of the reaction.

- i tion are the acrylic compounds such as acrylonitrile,

methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methylmethacrylate, ethyl methacrylate, the vinyl or vinylidene esters andothers such as vinyl acetate, vinylidene chloride, divinyl ether, vinylethyl ether, divinyl sulfide or allyl compounds such as allyl alcohol,allyl acetate and the like. These polymerizable monomers may be usedeither singly or in combination with one another.

The ceric salts which may be used in the practice of the process of thepresent invention include ceric nitrate, ceric sulfate, ceric ammoniumnitrate, ceric ammonium sulfate, ceric iodate, and the like.Additionally, one may make use of ceric dihexyl sulfosuccinate, cericdioctyl sulfosuccinate. These ceric salts are preferably dissolved ordispersed in an acidic material, preferably an inorganic acidicmaterial, prior to use on the cellulosic material. The pH of the cericsalt acid medium should be 3.5 or below. The acidic material may besulfuric acid, perchloric acid, nitric acid, and the like. Theconcentration of the eerie salt in the catalyst solution may vary fromabout l 10 to about 2X10- gram-mols per liter. The preferredconcentration is between about 1 10- and 1 10- gram-mols per liter.These concentrations may also be expressed as 00001-02 molar andpreferably 0.00l0.0l molar. The amount of catalyst solution which ispicked up by the material to be treated may vary from 40% to 200% byweight of the material. The preferred pickup is between about 75% and125% by weight based on the weight of the material.

In practicing the process of the present invention, a cellulosicmaterial such as woven cotton fabric is passed through a catalystsolution comprising a ceric salt dissolved in an acid solution wherebythe fabric becomes wetted and impregnated with the catalyst solution.While still in a wetted state, the impregnated web is introduced intothe vapor chamber and permitted to pass therethrough by use of aplurality of reverse rollers at a controlled residence time suflicientto enable the monomer vapors present in the chamber to graft-polymerizeon the cotton fabric. Thereafter, the web is removed from the vaporchamber and passed through a pair of squeeze rolls in order to removeany excess liquid on the fabric and then dried. In order to control theamount of graftpolymerization taking place on the cotton fabric, oneneed only control the residence time in the vapor chamber. Thereafter,one may neutralize the treated fabric upon its removal from the vaporchamber by passing the fabric through a neutralizing bath followed 'by asqueezing and drying operation.

Reference is made to the accompanying drawing which l is substantiallyself-explanatory, particularly in light of the which are composedpredominantly of cellulosic mate- 3 rials which have been subjected tochemical treatment such as regenerated cellulosic film (cellophane),viscose film, viscose rayon and the like. These cellulosic materialsmust be sufficiently porous and/or absorbent so as to allow liquids andgases to come into intimate contact instant disclosure. Reference tosaid drawing may be made in order to understand more completely theconcept of the present invention as set forth in the following examplesin which all parts are parts by weight unless otherwise indicated. Theseexamples are set forth primarily for the purpose of illustration and anyspecific enumeration of .detail contained therein should not beinterpreted as a limitation on the case except as is indicated in theaccompanying claims.

Example 1 A cotton fabric Web emanating from the source roll is passedthrough the catalyst bath containing 0.01 molar solution of cericammonium sulfate in a 0.1 molar solution of sulfric acid. The wetted webis then passed through the squeeze rolls, to give a wet pickup ofapproximately 110%, and then through the Bunsen valve into the vaportreating chamber filled with the vapor from a boilingacrylonitrile-water azeotrope. The rate of movement of the wetted webthrough the vapor treating chamber is such as to give the web aresidence time in the chamber of 2 minutes. The fabric is removed fromthe chamber, squeezed through the squeeze rolls, passed through theneutralizing bath to remove residual acrylonitrile, acid and ceric saltand is then dried. The weight increase of the fabric due to polymerdeposition is 21.7% The fabric thus treated showed outstandingresistance to degradation by microorganisms; showed no strength lossafter 6 weeks burial in soil whereas untreated fabric buried in the samesoil disintegration completely in less than 2 weeks.

Example 2 A web of regenerated cellulosic film is thoroughly washed withwater to remove the plasticizer. The film is soaked for 1 minute in a0.1 molar solution of ceric ammonium nitrate in 0.1 molar solution ofnitric acid. The web is then passed through the squeeze rolls and intothe vapor treating chamber filled with the vapor from a boiling methylacrylate-water azeotrope. The residence time in the chamber isapproximately 1 minute. Upon removal from the chamber, the film iswashed and dried. The weight increase due to polymer deposition is foundto be 52.8%. The treated film is more flexible than the untreated,unplasticized material. The polymer deposit is completely resistant toextraction by a wide variety of solvents.

It has been indicated hereinabove that the amount of polymer depositionon the cellulosic material may be controlled by varying the residencetime in the vapor chamber. This residence time can be varied over afairly substantial range. Periods of time as short as seconds may beused or the residence time can be controlled so as to maintain thecellulosic material in the vapor chamber for periods of 1 hour or even 2hours or more. When the residence time is too extended, the process maybecome cumbersome unless there is a particularly desirable reason formaintaining the residence time at more than 2 hours. For most practicalpurposes, residence times of between about 1 minute and minutes shouldbe sufficient.

It should be noted in the above examples that use is made of amonomer-water azeotrope. This is not imperative inasmuch as the monomercould be utilized alone without the benefit of any added water. It ispreferred, however, particularly for those monomers having a boilingpoint about 100 C., to use a small amount of water with the monomer soas to provide a lower boiling mixture. The amount of water that will beadded may be varied between about 10% and 25% by weight based on a totalweight of monomer and water.

The temperature of the vapor in the vapor chamber may be controlled byheating at the base of the chamber so as to put the monomer ormonomer-water mixture in the vapor phase at a temperature between aboutC. and 150 C. Preferably, one would operate between about 30 C. and 110C. When using the monomerwater azeotrope, one can increase the amount ofvapor of monomer in the chamber at temperatures below the normal boilingpoint of the monomer and as a consequence, it is sometimes advantageousto employ such a mixture.

The amount of monomer polymerized on the cellulosic base material may bevaried by controlling any one or all of (1) the amount of catalystpickup, (2) the temperature in the vapor chamber and (3) the residencetime of the material in the chamber.

We claim:

1. -A process comprising continuously contacting and Wetting acellulosic material with an acidic dispersion of a ceric salt, passingsaid wetted material through an atmosphere of a polymerizable monomerhaving a polymerizable CH =C group, wherein said monomer has a boilingpoint between about 20 C. and C. and is soluble in water to at least0.5%, in the vapor state, at a temperature elevated sufliciently tomaintain said monomer in the vapor phase and for a period of timesufiicient to graft-polymerize said monomer on said material whereinsaid process is carried out at substantially atmospheric pressure.

2. A process comprising continuously contacting and wetting cotton withan acidic dispersion of a ceric salt, passing said wetted cotton throughan atmosphere of a polymerizable monomer having a polymerizable group,wherein said monomer has a boiling point between about 20 C. and 150 C.and is soluble in water to at least 0.5%, in the vapor state, at atemperature elevated sulficiently to maintain said monomer in the vaporphase and for a period of time suflicient to graft-polymerize saidmonomer on said cotton wherein said process is carried out atsubstantially atmospheric pressure.

3. A process comprising continuously contacting and wetting cellulosicpaper with an acidic dispersion of a ceric salt, passing said wettedcellulosic paper through an atmosphere of a polymerizable monomer havinga polymerizable CH =C group, wherein said monomer has a boiling pointbetween about 20 C. and 150 C. and is soluble in water to at least 0.5%,in the vapor state, at a temperature elevated sufficiently to maintainsaid monomer in the vapor phase and for a period of time sufiicient tograft-polymerize said monomer on said cellulosic paper wherein saidprocess is carried out at substantially atmospheric pressure.

4. A process comprising continuously contacting and wetting regeneratedcellulosic film with an acidic dispersion of a ceric salt, passing saidwetted regenerated cellulosic film through an atmosphere of apolymerizable monomer having a polymerizable CH =C group, wherein saidmonomer has a boiling point between about 20 C. and 150 C. and issoluble in water to at least 0.5%, in the vapor state, at a temperatureelevated sufliciently to maintain said monomer in the vapor phase andfor a period of time sufiicient to graft-polymerize said monomer on saidregenerated cellulosic film wherein said process is carried out atsubstantially atmospheric pressure.

5. A process comprising continuously contacting and wetting rayon withan acidic dispersion of a ceric salt, passing said wetted rayon throughan atmosphere of a polymerizable monomer having a polymerizable about 20C. and 150 C. and is soluble in water to at least 0.5 in the vaporstate, at a temperature elevated sufficiently to maintain said monomerin the vapor phase and for a period of time suflicient tograft-polymerize said monomer on said rayon wherein said process iscarried out at substantially atmospheric pressure.

6. A process comprising continuously contacting and wetting a cellulosematerial with an acidic dispersion of a ceric salt, passing said wettedmaterial through an atmosphere of acrylonitrile, in the vapor state, ata temperature elevated sufiiciently to maintain said acrylonitrile inthe vapor phase and for a period of time sufiicient to graft-polymerizesaid acrylonitrile on said cellulosic material wherein said process iscarried out at substantially atmospheric pressure.

7. A process comprising continuously contacting and Wetting a cellulosicmaterial with an acidic dispersion of a ceric salt, passing said wettedmaterial through an atmosphere of methyl acrylate, in the vapor state,at a temperature elevated sufliciently to maintain said methyl acrylatein the vapor phase and for a period of time sufficient tograft-polymerize said methyl acrylate on said cellulosic materialwherein said process is carried out at substantially atmosphericpressure.

8. A process comprising continuously contacting and wetting a cellulosicmaterial with an acidic disperson of a ceric salt, passing said wettedmaterial through an atmosphere of ethyl acrylate, in the vapor state, ata temperature elevated sulficiently to maintain said ethyl acrylate inthe vapor phase and for a period of time sulficient to graft-polymerizesaid ethyl acrylate on said cellulosic material wherein said process iscarried out at substantially atmospheric pressure.

9. A process comprising continuously contacting and wetting cotton withan acidic dispersion of a ceric salt, passing said wetted materialthrough an atmosphere of acrylonitrile, in the vapor state, at atemperature elevated sufficiently to maintain said acrylonitrile in thevapor phase and for a period of time sufficient to graft-po1ymerize saidacrylonitrile on said cotton wherein said process is carried out atsubstantially atmospheric pressure.

10. A process comprising continuously contacting and Wetting cellulosicpaper. with an acidic dispersion of a ceric salt, passing said wettedmaterial through an atmosphere of methyl acrylate, in the vapor state,at a temperature elevated sutficiently to maintain said methyl acrylatein the vapor phase and for a period of time sufficient tograft-polymerize said methyl acrylate on said cellulosic paper whereinsaid process is carried out at substantially atmospheric pressure.

11. A process comprising continuously contacting and wetting cellulosicpaper with an acidic dispersion of a ceric salt, passing said wettedmaterial through an atmosphere of ethyl acrylate, in the vapor state, ata temperature elevated sufficiently to maintain said ethyl acrylate inthe vapor phase and for a period of time suflicient to graft-polymerizesaid ethyl acrylate on said cellulosic 35 paper wherein said process iscarried out at substantially atmospheric pressure.

12. A process comprising continuously contacting and wetting regeneratedcellulosic film with an acidic dispersion of a ceric salt, passing saidwetted material through an atmosphere of acrylonitrile, in the vaporstate, at a temperature elevated sufiiciently to maintain saidacrylonitrile in the vapor phase and for a period of time sufficient tograft-polymerize said acrylonitrile on said regenerated cellulosic filmwherein said process is carried out at substantially atmosphericpressure.

13. A process comprising continuously contacting and wetting regeneratedcellulosic film with an acidic disper- 10 sion of a ceric salt, passingsaid wetted material through an atmosphere of ethyl acrylate, in thevapor state, at a temperature elevated sufficiently to maintain saidethyl acrylate in the vapor phase and for a period of time su-fficientto graft-polymerize said ethyl acrylate on said regenerated cellulosicfilm wherein said process is carried out at substantially atmosphericpressure.

14. A process comprising continuously contacting and wetted rayon withan acidic dispersion of a ceric salt, passing said wetted materialthrough an atmosphere of acrylonitrile, in the vapor state, at atemperature elevated sufiiciently to maintain said acrylonitrile in thevapor phase and for a period of time sufficient to graft-polymerize saidacrylonitrile on said rayon wherein said process is carried out atsubstantially atmospheric pressure.

References Cited in the file of this patent UNITED STATES PATENTS2,434,106 Flood et a1 Jan. 6, 1948 2,719,132 Schweitzer Sept. 27, 19552,780,612 Grotenhuis Feb. 5, 1957 2,922,768 Mino et a1 J an. 26, 1960FOREIGN PATENTS 750,923 Great Britain June 20, 1956 OTHER REFERENCESBacon: Trans. Faraday Soc., vol. 42, pp. -155, Sept. 10, 1945.

1. A PROCESS COMPRISING CONTINUOUSLY CONTACTING AND WETTING A CELLULOSICMATERIAL WITH AN ACIDIC DISPERSION OF A CERIC SALT, PASSING SAID WETTEDMATERIAL THROUGH AN ATMOSPHERE OF A POLYMERIZABLE MONOMER HAVING APOLYMERIZABLE CH2=C< GROUP, WHEREIN SAID MONOMER HAS A BOILING POINTBETWEEN ABOUT 20*C. AND 150*C. AND IS SOLUBLE IN WATER TO AT LEAST 0.5%,IN THE VAPOR STATE, AT A TEMPERATURE ELEVATED SUFFICIENTLY TO MAINTAINSAID MONOMER IN THE VAPOR PHASE AND FOR A PERIOD OF TIME SUFFICIENT TOGRAFT-POLYMERIZE SAID MONOMER ON SAID MATERIAL WHEREIN SAID PROCESS ISCARRIED OUT AT SUBSTANTIALLY ATMOSPHERIC PRESSURE.